Equation of a common tangent to the curves and y2=8xandxy=−1is
A
3y = 9x +2
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B
y = 2x +1
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C
2y = x + 8
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D
y = x +2
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Solution
The correct option is D y = x +2 y2=8x,xy=−1LetP(t,−1t)beanypointonxy=−1Equationofthetangenttoxy=−1atP(t,−1t)isxy1+yx12=−1−xt+yt=−2y=xt2+(−2t)…(1)If(1)istangenttotheparabolay2=8xthem−2t=21/t2⇒t3=−1t=−1∴Commontangentisy=x+2